Treatment of sleep disordered breathing (SDB), such as obstructive sleep apnea (OSA), by continuous positive airway pressure (CPAP) mask systems involves the continuous delivery of air (or other breathable gas) pressurized above atmospheric pressure to the airways of a human or other mammalian patient via a conduit and a mask. Typically, the mask fits over the nose and/or mouth of the patient. Pressurized air flows to the mask and to the airways of the patient via the nose and/or mouth. As the patient exhales, carbon dioxide gas may collect in the mask. A washout vent in the mask or conduit discharges the exhaled gas from the mask to atmosphere.
Measures such as an Apnea-Hypopnea Index (AHI) are sometimes used to quantify the number of apneas and or hypopneas that a patient exhibits during a time period, as a measure of the severity of the condition. An AHI of about 5 is typically a low value, whereas an AHI of about 20 is a relatively high value. A patient with a high AHI value might need to change treatment, for example, to increase a CPAP treatment pressure.
Design of masks is a subtle art. Many patients find masks uncomfortable and they do not comply with therapy. Some masks are difficult to seal on the face, leading to patient tightening of retaining straps and this in turn can decrease comfort and lead to marks or sores on a patient's face. Some masks may exacerbate the problem they are trying to solve.